The emergence of new diseases such as SARS and avian influenza has increased the importance of infection-control practices by and for health care workers. Zamora and colleagues compared the effectiveness of 2 types of personal protective systems. Participants who used enhanced respiratory and contact precautions (E-RCP) were more likely to experience contamination than those who wore a system that included a powered air-purifying respirator (PAPR) and a second layer of protective equipment. The PAPR system, however, required more time to don and remove. In a related commentary, Conly recognizes the increased anxiety that heath care workers have about microbes that are transmitted by airborne or droplet routes. He reviews the experience of the SARS outbreak and the importance of infection-control techniques.